The present invention relates to topical compositions and methods for treating psoriasis. In particular, this invention relates to topical pharmaceutical compositions comprising a combination of active ingredients, and methods using the same, for treating psoriasis. More particularly, this invention relates to topical pharmaceutical compositions comprising a combination of a corticosteroid and a retinoid, and methods using the same, for treating psoriasis.
Psoriasis is a chronic skin disease affecting approximately about 2-4 percent of the population world-wide. Over seven million people in the United States are affected. While the pathogenesis of psoriasis has not yet been fully elucidated, significant evidence indicates that epidermal changes occur as a secondary response to cellular immune infiltrates in the skin. Psoriasis is characterized by discrete areas of skin inflammation with redness, thickening, intense scaling, and in some cases, itching. The disease has significant impact on the quality of life of affected individuals, both physically and psychologically. Today there is no cure for psoriasis, and treatment is directed at reducing the severity and extent of the psoriatic plaques and the related symptoms. The primary measurement of treatment success used by the U.S. Food and Drug Administration in evaluating products for the treatment of psoriasis is significant overall improvement in psoriasis severity based on Investigators Global Assessment.
Systemic therapy such as methotrexate, or biologics such as etanercept, adalimumab, infliximab, etc. are the preferred treatment when the skin involvement is extensive; e.g., ten percent of the body surface area or more. A large number of those suffering from psoriasis have less extensive disease, and topical medications are considered a safer and more prudent alternative in most of these cases. Among the topical therapies are anti-inflammatory corticosteroids; particularly, the super potent ones such as halobetasol propionate, vitamin D derivatives, such as calcipotriene, a retinoid known as tazarotene, and coal tar. Each of the topical therapies has some degree of effectiveness, but each has limitations in the degree of improvement of the psoriatic plaques that can be achieved or the occurrence of adverse effects.
Halobetasol propionate (a topical corticosteroid) is commercially available and has been used to treat psoriasis for about 20 years or more at strength of 0.05% in a variety of dosage forms such as creams and ointments. Halobetasol is quite effective in improving the signs and symptoms of psoriasis; however both local and systemic adverse effects limit its chronic use. Treatment duration is limited to 2 weeks by FDA, and signs and symptoms of psoriasis often rebound (worsen) following the end of treatment.
For many years tazarotene (a retinoid) has been commercially available and has been used to treat psoriasis topically as creams and gels of 0.05% and 0.1%. Tazarotene generally shows moderate effectiveness in psoriasis; however its use in psoriasis is severely limited by local skin irritation. Dermatologists treated psoriasis and achieved good clinical results using sequential therapy with a corticosteroid in the morning and tazarotene applied in the evening.
The need still exists for more effective and safer topical medicaments with reduced adverse effects for the management of psoriasis.